1. Technical Field
The present invention relates to an improved process and partible mold for vacuum molding a synthetic heat-resistant ceramic log for use in fireplaces and stoves.
2. Background Information
In various processes Which have been previously utilized for the manufacture of synthetic logs for use in natural gas, propane, and wood-burning fireplaces and stoves, such logs have heretofore been made of various types of high-temperature materials wherein the mold comprises an exterior shape around which the log is formed by drawing an interior vacuum around a pre-shaped sculpted pre-form. The high-temperature materials are usually deposited on the exterior of the pre-form. The pre-form is contained within the mold interior and a vacuum is drawn interiorly from within the pre-form to shape the simulated log on the exterior surface of the pre-form. Such logs are frequently made from various heat-resistant materials, such as ceramic fibers mixed with high-density materials of a cementitious nature, which are able to resist high-temperature conditions for relatively long periods of time without distortion or damage to the synthetic log. Such synthetic logs are normally made with finely-sculpted details which produce natural-looking fire effects simulating wood burning logs.
Open burning, which includes wood-burning fireplaces, is being increasingly prohibited due to regulations governing air pollution. In addition, the cost of natural wood for use in fireplaces and wood-burning stoves has been steadily increasing. Thus, the use of synthetic ceramic logs in such combustion environments using clean burning fuels is becoming increasingly important without the deleterious effects of natural wood-burning.
Synthetic logs have been made available in both natural gas and propane burning gas sets as well as for use in wood-burning fireplaces and stoves to simulate the effects of wood burning. Such logs have been formed of ceramic fibers which will withstand extremely high temperatures over lengthy periods of time and provide both heating and aesthetic effects. The logs normally consist of materials which are resistant to thermal shock and which will not crack, break or change color when heated over lengthy time periods. Such logs are frequently formed to glow with special effects where flame touches the logs. The ceramic logs may be used in fireplaces and stoves wherein a plurality of such members is arranged in a grate or burner pan which is normally fully vented. The logs are made with heat-resistant colors and of varying densities adapted to withstand continuous temperatures ranging from about 800.degree. to 1600.degree. F. without damage thereto. It is highly desirable that the logs have a low coefficient of thermal expansion and be capable of rapid thermal changes without appreciable thermal shock which will cause their cracking or breaking during both short-term and long-term heating cycles.